The polymerase chain reaction has rapidly become an indispensable tool of molecular biology. For new agents, searching for the most effective thermal cycle for lysis, quenching, and annealing of the nucleotide is a time-consuming process. The instrumentation being developed will streamline the search process by automatically cycling the reactants through predetermined temperature profiles. The technology employs PC-- based computer control of five independent thermoelectric modules, and is readily expandable to greater numbers of reactant chambers.